Manufacture of deep, narrow, hollow articles

ABSTRACT

Deep, narrow, hollow articles are made of metal by explosive forming a shallow vessel, trimming the sheet to the desired shape at the edges thereof, dividing it, reorienting the divided members so that the flanges of the formed sheet which were opposite each other, are now in juxtaposition, and joining the contacting edges from end to end thereof.

llnited States Patent 1 Umlholtz et al.

[111 3,757,411 Sept. 11, 1973 MANUFACTURE OF DEEP, NARROW,

HOLLOW ARTICLES [76] Inventors: Franklyn G. Umholtz, Box 16,

Shutesbury, Mass. 01502; Donald E. Scott, RED. 3, Juggler Meadow Rd., Amherst, Mass. 01002; James M. Douglas, Star Rt. No. 1, Montague, Mass.

[22] Filed: Nov. 4, 1971 [21] Appl. No.: 195,668

[52] U.S. CI. 29/416, 29/421 E, 29/425, 29/463, 9/6, 113/116 BB [51] Int. Cl B63b 3/06 [58] Field of Search 29/463, 416, 421 E, 29/425; 113/116 BB, 120 C, 120 H, 120 QA; 229/D1G. 9; 9/6

I56] References Cited UNITED STATES PATENTS 12/1962 Geary 29/463 Filler 29/421 E Johnson et al 29/463 FOREIGN PATENTS OR APPLICATlONS 385,587 3/1931 Great Britain 29/425 1,251,164 12/1960 France 824,495 11/1937 France 9/6 Primary Examiner-Richard J. Herbst AttorneyCharles R. Fay

[57] ABSTRACT Deep, narrow, hollow articles are made of metal by explosive forming a shallow vessel, trimming the sheet to the desired shape at the edges thereof, dividing it, reorienting the divided members so that the flanges of the formed sheet which were opposite each other, are now in juxtaposition, and joining the contacting edges from end to end thereof.

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MANUFACTURE OF DEEP, NARROW, HOLLOW ARTICLES BACKGROUND OF THE INVENTION The manufacture of deep, narrow,-hollow articles of the type which do not lend themselves to easy deep drawing, e.g., a displacement hull, or sailboat hull, have been made by assembling a plurality of sheets of metal and riveting them together in the desired shape or by forming the same of fiber glass inside a female form. Also of course traditionally displacement hulls have been made very laboriously of wood. This invention contemplates making such articles, e.g., displacement hulls, essentially in one piece or more accurately in two or more separate pieces welded together.

SUMMARY OF THE INVENTION A flat sheet of material is explosive formed against a shallow female die of predetermined correct shape. This leaves a shallowly dished central portion of a sheet of material having a surrounding flange. This flange is then cut to desired shape and in the case of a displacement hull it is cut at the opposite edges of the long sides of an elongated sheet,'being shaped to form a keel.

The formed sheet is then divided centrally longitudinally and the opposite shallow formed members including the keels are rotated (reoriented) and placed together, and the entire length of the two sheets welded together forming the bow, keel, and stem.

This forms a two-piece welded, essentially one-piece, sheet metal boat hull or other deep, narrow articles which is either impossible or very difficult to make in a single sheet by deep drawing of the metal.

The same method can be used to result in approximately the same article in more than twoparts if this should be found advantageous ordesirous but if a sheet of metal is available which is wide enough, then a hull of any small or intermediate size is easily made in the manner stated and this has the result of providing a completely leakproof hull with very few maintenance problems, and it also greatly'lessens the expense of making the hull by conventional means, i.e., riveting sheets of material, moldingof fiber glass, or forming of wood.

Reference is made to a publication by Arthur A. Ezra, Ph.D., Center for High Energy Forming at the University of Denver entitled THE EXPLOSIVE FORMING OF METALS. This paper in-and of itself explains explosive forming and also contains a consid erable bibliography with relation to the subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in side elevation of the finished article;

FIG. 2 is a view in end'elevation thereof looking in the direction of arrow 2 in FIG. I;

FIG. 3 is a top plan view of the article;

FIG. 4 is a plan view of the explosion formed sheet showing in dotted lines the final cutting to shape;

FIG. 5 is a view inside elevation of the blank of FIG. 4 looking in the direction of arrow 5 in-FIG. 4;

FIG. 6 is a section on line 6-6, of FIG. 5;

FIG. 7 is a side view of one of the halves of the formed sheet;

FIG. 8 is a sectional view showing the two parts made from the formed sheet of FIG. 4 as they appear divided,

reversed, and welded to form the complete article shown in FIGS. 1, 2 and 3, and

FIGS. 9 and 10 illustrate a different form of the invention.

PREFERRED EMBODIMENT OF THE INVENTION The invention is disclosed as relating to displacement hulls, i.e., sailboat hulls, but the invention can be practiced to form any deep, narrow, hollow article of metal which does not lend itself to easy deep drawing. FIGS. 1,.2 and 3 show the article which is to be formed. There is a hull having a bow portion 10 and a stern portion 12, which may be cut off on dotted lines 14 in FIG. 3 to provide for the application of a transom thereto. The hull has a keel 16 and is made of two light but reoriented parts 18 and 20 which are welded together along the entire conjoining edge thereof 22, the weld then being ground and polished so that the hull virtually is a one-piece article of considerable depth which is narrow and contains no rivets.

It will be seen from the conformation of this article that it is too narrow for easy deep drawing of the metal regardless of what kind of metal is used, and in this case aluminum of a certain nature is preferably utilized as will be clear to those skilled in the art.

A flat sheet which may be rectangular or have the outline indicated at 24, 26 in FIG. 4 is placed in flat condition on a female mold previously prepared as to the desired conformation. The same is then submerged, and a charge is exploded in proximity theretoin'the fluid material, generally as explained by Dr. Ezra in the above mentioned article. This then results in a very shallow dish shown in side elevation in FIG. 5 and shaded in FIG. 4 to illustrate the bowl shape.

The shallow bowl shape is shown at approximately midpoint of the blank in FIG. 6, and it will be seen that it has a completely surrounding flange as at 28, 30 and is deformed in the area at 32 to form a shallow, elongated bowl.

Referring now to FIG. 4, the flanges are then cut out along the dotted lines 34 and this then forms a shallow bowl with a keel outline 36, 36, bow outline 38, 38, and stern outline 40, 40.

When this outline has been achieved, the bowl is then divided exactly in two along the broken line which is indicated at 42, FIG. 4, and this results in two complementary parts such as shown generally at 44 in FIG. 7, the same having a generally shallow indentation at 46, 48, and keel 36, stern portion 40, and bow portion 38.

These two parts are then assembled as shown in FIG. 8 with the two keel portions 3.6, 36 together and adjoining also along the entire length of the bow and stem, it being seen that the bowportions and stem portions coincide with each other. Then the entire length of the device centrally thereof is welded from stem .to stem.

The article shown in FIGS. 1, 2 and 3 is now completed. Essentially the deep, narrow, hollow article thus formed is formed from two shallowly deformed elements, made together from a single blank. This is most efficiently done by explosive forming because of the relatively large size of the original blank as for instance if a 27' displacement hull is being made. Longer hills demand wider as well as longer blanks and smaller hulls may be easily made depending upon the hull design, etc., the design of displacement hulls of all lengths being well known to those skilled in the art.

ln explanation, it is pointed out that in explosion molding the entire periphery of a sheet must be clamped. Thus if a bow only were being made there would be a partition at the end thereof away from the cutwater which would have to be removed before the bow portion is joined to the stem portion. The stem portion may have the same kind of a partition which also has to be removed prior to joining the parts together.

However, FIGS. 9 and 10 show another aspect of the invention wherein a similar blank is explosion formed as before but in this case the ends at 50, 52 are alike but reversed. By cutting longitudinally along line 54, and transversly along line 56 four bow halves or four stern halves may be obtained. Then by the same reorientation of the parts, i.e., rotating the respective halves into correct position and welding, two stern or two bow portions can be produced.

We claim:

1. The method of forming a deep, hollow, open top ships hull comprising the steps of explosion forming a wide, shallow bowl-like blank, the width being greater than the depth thereof, having a substantially flat rim, cutting the rim to form a pair of keel parts at opposite sides of the blank, dividing the blank centrally mid-way of the keel parts into two like but reversed complementary parts, placing the rims and keel parts of the two parts together, and joining the same from end to end thereof.

l t II 

1. The method of forming a deep, hollow, open top ship''s hull comprising the steps of explosion forming a wide, shallow bowllike blank, the width being greater than the depth thereof, having a substantially flat rim, cutting the rim to form a pair of keel parts at opposite sides of the blank, dividing the blank centrally mid-way of the keel parts into two like but reversed complementary parts, placing the rims and keel parts of the two parts together, and joining the same from end to end thereof. 